document.write( "Question 1157110: Anna can do a piece of work in 12 days. Beth can do the same work in 15 days. Charles can also do the same piece of work in 30 days. Anna starts the work and Beth joins her after 3 days. 3 days before the work is completed Anna leaves and Charles joins the work. In how many days will the work be completed? \n" ); document.write( "
Algebra.Com's Answer #779918 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
You are given their rates of working:
\n" ); document.write( "Anna: [ 1 job ] / [ 12 days ]
\n" ); document.write( "Beth: [ 1 job ] / [ 15 days ]
\n" ); document.write( "Charles [ 1 job ] / [ 30 days ]
\n" ); document.write( "------------------------------------
\n" ); document.write( "Anna starts working alone and
\n" ); document.write( "works for 3 days. In 3 days she
\n" ); document.write( "does this fraction of the job:
\n" ); document.write( "\"+%28+1%2F12+%29%2A3+=+1%2F4+\"
\n" ); document.write( "There is \"+3%2F4+\" of the job left
\n" ); document.write( "-------------------------------------
\n" ); document.write( "Anna and Beth then work together for
\n" ); document.write( "an unknown number of days.
\n" ); document.write( "Let \"+d+\" = the number of days they work together
\n" ); document.write( "Their rate of working together is:
\n" ); document.write( "\"+1%2F12+%2B+1%2F15+=+5%2F60+%2B+4%2F60+\"
\n" ); document.write( "\"+1%2F12+%2B+1%2F15+=+9%2F60+\"
\n" ); document.write( "\"+9%2F60+=+3%2F20+\"
\n" ); document.write( "The fraction of the remaining work they get done is:
\n" ); document.write( "\"+%28+3%2F20+%29%2Ad%2A%283%2F4%29+=+%28+9%2F80+%29%2Ad+\"
\n" ); document.write( "So now \"+1%2F4+%2B+%28+9%2F80+%29%2Ad++\" is done
\n" ); document.write( "\"+1+-+1%2F4+-+%28+9%2F80+%29%2Ad+=+3%2F4+-+%28+9%2F80+%29%2Ad+\" is
\n" ); document.write( "the fraction left to do
\n" ); document.write( "---------------------------
\n" ); document.write( "Now for 3 days, Charles and Beth work together
\n" ); document.write( "and they finish the job
\n" ); document.write( "Add their rates of working
\n" ); document.write( "\"+1%2F15+%2B+1%2F30+=+%28+3%2F4+-+%28+9%2F80+%29%2Ad+%29+%2F+3+\"
\n" ); document.write( "\"+1%2F15+%2B+1%2F30+=+1%2F4+-+%28+3d+%29+%2F+80+\"
\n" ); document.write( "\"+2%2F30+%2B+1%2F30+=+20%2F80+-+%283d%29%2F80+\"
\n" ); document.write( "\"+3%2F30+=+%28+20+-+3d+%29+%2F+80+\"
\n" ); document.write( "\"+1%2F10+=+%28+20+-+3d+%29%2F+80+\"
\n" ); document.write( "Multiply both sides by \"+80+\"
\n" ); document.write( "\"+8+=+20+-+3d+\"
\n" ); document.write( "\"+3d+=+12+\"
\n" ); document.write( "\"+d+=+4+\"
\n" ); document.write( "So Anna and Beth worked together for \"+4+\" days
\n" ); document.write( "------------------------------
\n" ); document.write( "Add up the days they all worked:
\n" ); document.write( "Anna alone: 3 days
\n" ); document.write( "Anna & Beth: 4 days
\n" ); document.write( "Charles and Beth: 3 days
\n" ); document.write( "\"+3+%2B+4+%2B+3+=+10+\"
\n" ); document.write( "They finish the work in 10 days
\n" ); document.write( "------------------------------------
\n" ); document.write( "Check my math and get a 2nd opinion if needed\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );